The present invention relates generally to a vehicle seat having a side air bag contained therein and in particular to such a seat with a force concentrator adjacent the air bag to concentrate the force of the inflating air bag at a designed seam in the trim cover to ensure deployment of the air bag through the seam.
In recent years, automobile manufacturers have directed increasing attention to providing improved side impact protection for vehicle occupants. One method of doing so is to provide an inflatable side air bag mounted to the vehicle seat and deployable between the seat occupant and the adjacent vehicle door or body structure. The side air bag (SAB) functions to dampen and distribute the impact load to reduce occupant injuries.
Generally, seat mounted SAB systems fall into two different categories, known as class A and class B. A class A side air bag deploys from a visible, discrete door on the outboard side of the seat back or seat cushion bolster. A class B side air bag is stowed beneath the seat trim cover and is designed to deploy through the trim cover. An advantage of the class A side air bag, is that deployment of the air bag through a door uses technology that has already been developed for frontal air bags in steering wheels and instrument panels. The technology for providing consistent and repeatable deployment of the air bag through the door is well developed. A disadvantage of a class A side air bag is that the air bag location is generally limited to the side of the seat so that the visible door is not a part of the seating surface engaged by a seat occupant. If it is desired for the air bag to deploy through the front corner of the seat back, such as the location of a bolster seam, a class A side air bag cannot be used. Rather, a class B side air bag must be used in which the air bag is underneath the seat back trim cover, and typically beneath a foam pad, where it does not adversely impact the seat comfort. However, with a class B side air bag, there are considerably more variables involved in providing consistent air bag deployment and in meeting the desired air bag in-position timing.
The seat trim cover provides numerous variables affecting air bag deployment. The trim cover fabric type, such as cloth, leather, vinyl, etc. and combinations of these various types, all behave differently and have different tensile and tear strengths. In addition, different materials of the same types, such as different cloth fabrics have different tensile strengths, tear strengths, weave, nap direction, etc. which can affect the manner in which an air bag deploys through the trim cover if the trim cover material is ruptured to deploy the air bag. Other variables introduced by the trim cover include the strength of the trim cover scrim layer or backing and the strength of the thin layer of foam that is typically laminated to the trim cover fabric.
Wear of the trim cover over time and trim cover damage by cutting, puncturing, cigarette burns, etc., also introduce variables in air bag deployment. For example, a cut in the trim cover at a location other than the intended deployment can cause the trim cover to rupture at the wrong location, resulting in the air bag being out of position.
Other variations in the deployment can be introduced by the density and type of the seat foam pad, the presence or absence of a border wire embedded in the foam pad, the trim cover attachment locations and types of attachments and misalignment of the trim cover on the seat back.
To reduce or eliminate the effects of the above variables, it is proposed to deploy a class B type SAB through a seam in the trim cover due to thread failure. Variables affecting the seam include the seam type, number of stitches per inch, thread strength, the seam arrangement, styling, welting, seam wear, ultraviolet exposure, etc. Most of these variables can be controlled in the design of the trim cover. As a result, greater deployment consistency can be achieved with deployment through a trim cover seam. However, even with designed deployment through a seam, the trim cover will introduce variations in SAB deployment.
It is an object of the present invention to design a vehicle seat having a side air bag with great air bag deployment consistency.
It is a further object of the invention to eliminate or minimize variability in air bag deployment introduced by the trim cover.
It is yet another object of the invention to provide a seat with a side air bag in which variability arising over time, caused by wear of and/or damage to the trim cover, does not affect the air bag deployment.